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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20260413192030.3275825-1-ziy@nvidia.com> <20260413192030.3275825-7-ziy@nvidia.com> From: Baolin Wang In-Reply-To: <20260413192030.3275825-7-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 5E3264000E X-Stat-Signature: o7hojc69c51kcyddqso3gc4a9kp9gxom X-HE-Tag: 1776236000-463039 X-HE-Meta: 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 5Hv4Mk8/ ZSrAj0lXM5h58LrV8yTlzL4HmoeUtcs8JdBQ2QKW8bWEeuNM7yPyNNNzLVa/+658mn6YCj+cbTMIqeDf+uMfR9H2UJKs/DyUKsYi7jDxAvUuqsqpnn5ztYGEyRlcgEBkiczVyvJ76ynK+c8p/8wdj+VKbDhQPvYcE2A84HaNARRfIlFJdBkuEBQUsHPxFeS0mNHSbxDFHslrPJenurZROhmIIvXoiRFnXGfkMcsMc+2zPDFl6OJR5c2cselQb95CO7H9UiOPXFsHag/+8/WbWATajT4t8rV8WGi81lGiL5EtSqPxT662sx+k1/A8euR/iP/krvauhNDkq+7U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/14/26 3:20 AM, Zi Yan wrote: > They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without > large folio support, so that read-only THPs created in these FSes are not > seen by the FSes when the underlying fd becomes writable. Now read-only PMD > THPs only appear in a FS with large folio support and the supported orders > include PMD_ORDRE. > > READ_ONLY_THP_FOR_FS was using mapping->nr_thps, inode->i_writecount, and > smp_mb() to prevent writes to a read-only THP and collapsing writable > folios into a THP. In collapse_file(), mapping->nr_thps is increased, then > smp_mb(), and if inode->i_writecount > 0, collapse is stopped, while > do_dentry_open() first increases inode->i_writecount, then a full memory > fence, and if mapping->nr_thps > 0, all read-only THPs are truncated. > > Now this mechanism can be removed along with READ_ONLY_THP_FOR_FS code, > since a dirty folio check has been added after try_to_unmap() and > try_to_unmap_flush() in collapse_file() to make sure no writable folio can > be collapsed. > > Signed-off-by: Zi Yan > --- Thanks. LGTM. Reviewed-by: Baolin Wang